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Home Gardener’s Guide

vernonia lettermannii

vernonia lettermannii

Horticulture Tips for September

Oklahoma Cooperative Extension Service

Division of Agricultural Sciences and Natural Resources

Oklahoma State University




David Hillock



  • Watch for fall specials at garden centers and nurseries since fall is a great time for planting many ornamentals.
  • Choose spring flowering bulbs as soon as available.
  • Plant cool-season annuals like pansies, ornamental cabbage or kale, snapdragons and dusty miller when temperatures begin to cool.
  • Watch for and control any late infestations of tree webworms.
  • Twig girdler insects should be controlled if large numbers of small branches of elms, pecans or persimmons are uniformly girdled from the tree and fall to the ground.
  • Begin to reduce the amount of light on outside tropical houseplants by placing them under shade trees before bringing them indoors for the winter.


  • You have all of September to plant cool-season vegetables like spinach, leaf lettuce, mustard and radishes, and until the middle of September to plant rutabagas, Swiss chard, garlic and turnips.


  • Last nitrogen fertilizer application of the year on warm-season grasses should be applied no later than September 15. (HLA-6420)
  • Winter broadleaf weeds like dandelion will begin to emerge in late September, which is also the best time to control them with a 2, 4-D type herbicide.
  • If pre-emergent control of winter-annual weeds (henbit, chickweed, annual bluegrass, etc.) is desired in lawns, the application should be completed by the second week of September. Note: Do not treat areas that will be seeded in the fall.
  • Continue bermudagrass spray program with glyphosate products for areas being converted over to tall fescue this fall.
  • Plan to seed bluegrass, fescue or ryegrass as needed in shady areas in mid- to late-September. Fall is the best time to establish cool-season lawns (HLA-6419).
  • White grub damage can become visible this month. Apply appropriate soil insecticide if white grubs are a problem (EPP-7306). Water product into soil.


Late Summer Color

David Hillock

As we near the end of summer many plants in the landscape are tired, but in spite of the heat there are several landscape plants putting on quite the show.  Below are just a few annuals and perennials growing at The Botanic Garden at OSU.


Natural Air Filters

David Hillock

As a society, more and more of us spend many hours indoors due to work, family etc. Because we spend so much time indoors, we often want to make our living/work spaces more pleasant and attractive. One of the first things we turn to are plants. However, indoor plants provide us with more than just decoration, they act as air filters purifying the air round the clock.

Today there are many chemicals in the air around us that we can’t even see, but may be affecting our health. They come from things like carpeting, paint, finishes or glues, furniture and plastic. Many of these products contain chemicals like benzene, formaldehyde and trichloroethylene or TCE.

Many indoor plants have been tested by NASA researchers for their air purifying abilities. NASA has found that many houseplants actually absorb these chemicals from the air leaving it cleaner for us to breathe. Living plants can make a big difference in our interior environment. All it takes is about eight to fifteen plants in an average size home.

NASA has also found that some plants are better air filters than others. The Chinese evergreen, English ivy, Mother-in-law’s tongue and Dracaena marginata are just a few. The corn plant is another excellent example of one that will clean our air. All of these plants made NASA’s top ten list. Here’s the entire list:

NASA’s Top Ten Plants Most Effective in Removing Formaldehyde, Benzene and Carbon Monoxide from the Air

Common Name Scientific Name
Bamboo Palm Chamaedorea seifritzii
Chinese Evergreen Aglaonema modestum
English Ivy Hedera helix
Gerbera Daisy Gerbera jamesonii
Janet Craig Dracaena ‘Janet Craig’
Marginata Dracaena marginata
Mass cane/Corn Plant Dracaena massangeana
Mother-in-Law’s Tongue Sansevieria laurentii
Pot Mum Chrysanthemum morifolium
Peace Lily Spathiphyllum ‘Mauna Loa’
Warnecki Dracaena ‘Warneckei’


Moving Plants Indoors for Winter

David Hillock

If you brought houseplants out into the summer sunshine, you want to start thinking about preparing them for their return journey indoors late this month. As a general rule, you will want to move houseplants indoors around the time that the outside temperature is about the same as the indoor temperature. This will give plants a chance to adjust to the indoor climate before you turn on the heat and avoid unnecessary cold damage to tropicals.

Moving a plant directly from its perch on the sunny patio to its winter home in the dark living room is not advisable. You will shock the plant with the drastic change in light conditions. Instead, acclimate the plant or slowly adjust it to lower light levels. Do this by moving plants to more and more heavily shaded areas over the course of a week before finally bringing it inside.

Be sure to inspect plants for insects and diseases and treat accordingly before moving indoors. Spraying leaves and stems with a steady stream of water will help get rid of many insects. You can also wipe stems and leaves down with a soft, damp cloth. Constant drenching of the soil in the pot will also help drive out insects that have taken up residence in the soil. If the pot is small enough, you might also remove the plant from the pot to look for insects and simply remove them by hand. Plants can also be repotted to make sure there are no unwanted pests. Insecticidal soaps are safe and can be used on many houseplants; if persistent pests are suspected spray with an insecticidal soap. More than one application may be necessary. Read and follow all label directions!


Free Resources for Youth Horticulture Education

Shelley Mitchell

The Nutrients for Life Foundation has a website ( with lists of free resources that you can download or have mailed to you. Their materials are about soil health and fertilizers. Free resources include curriculum for different levels, kindergarten to high school; videos; magnets; posters; bumper stickers; rulers; and postcards. Multiple copies can be ordered free of charge.

The International Society for Horticultural Science has created a publication, brochure and website ( to explain horticulture and its value to the general public. With plenty of photos, diagrams and graphs, “Harvesting the Sun: A Profile of World Horticulture” provides basic information regarding production, food handling and safety, pest and disease control, career paths in horticulture, human health and future global outlooks. The publication is an excellent resource to pull from when making posters, writing reports or sharing something new with a group of young people. The full report can be downloaded for free, as can individual chapters.

The free Junior Plant Scientist program was developed at Michigan State University. Ten different plant exploration modules cover topics such as plant names, taxonomy, plant uses, diversity of plants, and plant life cycles, and can be downloaded from Registration is free, and certificates are awarded to those youth who complete all 10 modules. These can be done individually or as part of a group.

Free manuals from “Got Dirt?” include: Garden toolkit for implementing youth gardens, Cold Frame manual, Container Gardening manual, Microfarm manual and Simple Raised Bed instructions. All can be downloaded from .